1. Field of the Invention
The present invention relates to an image pickup unit for an endoscope having a movable lens drive section which is disposed at a distal end portion of an endoscope insertion portion and moves some or all of objective lenses.
2. Description of the Related Art
Endoscopes which can be introduced from outside of a living body or a structure into an inside and include an image pickup unit for picking up an optical image are utilized in, e.g., fields of medicine and industry in order to observe a spot difficult to observe, such as an inside of a living body or an inside of a structure.
An image pickup unit of an endoscope includes an objective lens which forms an object image and an image pickup device (typically, a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor) sensor) which is disposed at an image formation surface of the objective lens.
For example, Japanese Patent Application Laid-Open Publication No. 2007-229155 discloses an image pickup unit for an endoscope which has a movable lens among objective lenses and is provided with a function of changing a photographing magnification by moving the movable lens in an optical axis direction (a variable-power function or a zoom function).
In a technique disclosed in Japanese Patent Application Laid-Open Publication No. 2007-229155, the image pickup unit for an endoscope is configured to include a lens barrel portion including a movable lens holding barrel which holds the movable lens and is capable of moving to advance and retract in the optical axis direction and an image pickup device and a drive mechanism portion which is disposed at a side portion of the lens barrel portion. An arm portion protruding outwardly in a radial direction is provided at the movable lens holding barrel. The drive mechanism portion is configured to drive the movable lens holding barrel in the optical axis direction by pushing and pulling the arm portion. The lens barrel portion and the drive mechanism portion of the image pickup unit for an endoscope are shaped to extend in a direction toward a proximal end separately from each other.